Autocapture pacing/sensing configuration

Abstract

A cardiac pacing system that enhances the ability of a cardiac pacer to automatically detect whether a pacing stimulus results in heart capture or contraction. The cardiac pacing system includes a pacing circuit that attenuates polarization voltages or “afterpotential” which develop at the heart tissue/electrode interface following the delivery of a stimulus to the heart tissue, which thereby allows the pacing electrodes to be utilized to sense an evoked response to the pacing stimulus. The cardiac pacing system utilizes the pacing electrodes to sense an evoked response, thereby eliminating the necessity for an indifferent electrode to sense an evoked response. The present invention allows accurate detection of an evoked response of the heart, to thereby determine whether each pacing stimulus results in capture.

1. A cardiac pacing system for use with unipolar or bipolar atrial and ventricular pacing and sensing leads, said cardiac pacing system including:
 (a) at least an atrial lead having atrial electrodes comprising an atrial tip electrode and an atrial ring electrode electrically coupled thereto; 
 (b) at least a ventricular lead having ventricular electrodes comprising a ventricle tip electrode and a ventricle ring electrode electrically coupled thereto; 
 (c) pacing means for providing a pacing stimulus to at least one of an atrium or ventricle of a heart, said pacing means electrically coupled to at least one of said atrial lead and said ventricular lead; 
 (d) sensing means for sensing a response evoked by the pacing stimulus, said sensing means electrically coupled to at least one of said atrial lead and said ventricular lead said sensing means including multiple independent blanking switches corresponding to independent electrodes; 
 (e) an indifferent electrode and an electrically conductive can that contains the pacing and sensing means, said indifferent electrode being positioned on the can; 
 (f) afterpotential attenuation means for attenuating afterpotentials which result due to the application of the pacing stimulus to the heart by said cardiac pacing system, said afterpotential attenuation means being electrically coupled to said pacing means and including first coupling capacitor means for attenuating afterpotential operatively coupled to second coupling capacitor means for blocking DC components, and also including switching means for selectively coupling said second coupling capacitor means in series with said first coupling capacitor means so as to reduce the effective capacitance of said second coupling capacitor means, said system having a combined reduced coupling capacitance of less than 5 microfarads; and 
 (g) wherein the sensing means is adapted to selectively sense evoked responses between all combinations of any two of said electrodes. 
 
   
   
     2. A cardiac pacing system as in  claim 1  wherein the signal associated with the evoked response is sensed between the atrial tip electrode and the indifferent electrode. 
   
   
     3. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the ventricular tip electrode. 
   
   
     4. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and the indifferent electrode. 
   
   
     5. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the ventricular tip electrode and the indifferent electrode. 
   
   
     6. A cardiac pacing system as recited in  claim 1 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the indifferent electrode positioned on a can of the cardiac pacer and electrically coupled to the cardiac pacer. 
   
   
     7. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and one of the ventricular electrodes. 
   
   
     8. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the atrial tip electrode and one of the ventricular electrodes. 
   
   
     9. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the atrial tip electrode. 
   
   
     10. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the atrial tip electrode arid the electrically conductive housing of the cardiac pacing system. 
   
   
     11. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and the electrically conductive housing of the cardiac pacing system. 
   
   
     12. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and the ventricular tip electrode. 
   
   
     13. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the electrically conductive housing of the cardiac pacing system. 
   
   
     14. A cardiac pacing system as in  claim 1 , wherein the signal associated with the evoked response is sensed between the ventricular tip electrode and the electrically conductive housing of the cardiac pacing system. 
   
   
     15. A cardiac pacing system as in  claim 1 , wherein said first coupling capacitor means has a substantially smaller capacitance than said second coupling capacitor means. 
   
   
     16. A cardiac pacing system as in  claim 1 , wherein said second coupling capacitor means has a capacitance ranging from 10–40 microfarads, and said first coupling capacitor means has a capacitance less than 5 microfarads. 
   
   
     17. A cardiac pacing system for use with unipolar or bipolar atrial and ventricular pacing and sensing leads, said cardiac pacing system including:
 (a) at least an atrial lead having atrial electrodes comprising an atrial tip electrode and an atrial ring electrode electrically coupled thereto; 
 (b) at least a ventricular lead having ventricular electrodes comprising a ventricle tip electrode and a ventricle ring electrode electrically coupled thereto; 
 (c) a pacing circuit including a pacing charge storage capacitor that provides a pacing stimulus to at least one off an atrium or ventricle of a heart, said pacing circuit electrically coupled to at least one of said atrial lead and said ventricular lead; 
 (d) a sensing circuit that senses a response evoked by the pacing stimulus, said sensing circuit electrically coupled to at least one of said atrial lead and said ventricular lead, said sensing circuit including multiple independent blanking switches corresponding to independent electrodes; 
 (e) an indifferent electrode and an electrically conductive can that contains the pacing and sensing means, said indifferent electrode being positioned on the can; 
 (f) a plurality of coupling capacitors electrically coupled together including a first coupling capacitor that attenuates afterpotential, operatively coupled to a second coupling capacitor that blocks DC components, and also includes switches for selectively coupling said second coupling capacitor in series with said first coupling capacitor so as to reduce the effective capacitance of said second coupling capacitor, wherein a capacitance of the capacitors coupled together has a combined reduced capacitance of less than 5 microfarads wherein the combined reduced capacitance of less than 5 microfarads attenuates afterpotentials which result due to the application of the pacing stimulus to the heart by said cardiac pacing system, said capacitors being electrically coupled to said pacing circuit; and 
 (g) wherein the sensing circuit is adapted to selectively sense evoked responses between all combinations of any two of said electrodes. 
 
   
   
     18. A cardiac pacing system as in  claim 17  wherein the signal associated with the evoked response is sensed between the atrial tip electrode and the indifferent electrode. 
   
   
     19. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the ventricular tip electrode. 
   
   
     20. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and the indifferent electrode. 
   
   
     21. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the ventricular tip electrode and the indifferent electrode. 
   
   
     22. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the indifferent electrode. 
   
   
     23. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and one of the ventricular electrodes. 
   
   
     24. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the atrial tip electrode and one of the ventricular, electrodes. 
   
   
     25. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the atrial tip electrode. 
   
   
     26. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the atrial tip electrode and the electrically conductive housing of the cardiac pacing system. 
   
   
     27. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and the electrically conductive housing of the cardiac pacing system. 
   
   
     28. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the atrial ring electrode and ventricular tip electrode. 
   
   
     29. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the ventricular ring electrode and the electrically conductive housing of the cardiac pacing system. 
   
   
     30. A cardiac pacing system as in  claim 17 , wherein the signal associated with the evoked response is sensed between the ventricular tip electrode and the electrically conductive housing of the cardiac pacing system. 
   
   
     31. A cardiac pacing system as in  claim 17 , wherein said first coupling capacitor has a substantially smaller capacitance than said second coupling capacitor. 
   
   
     32. A cardiac pacing system as in  claim 17 , wherein said second coupling capacitor has a capacitance ranging from 10–40 microfarads, and said first coupling capacitor has a capacitance less than 5 microfarads.